Apparatus for controlling the electron beam in a television camera tube

Abstract

A camera tube device for use in, for example, a television camera comprises a cathode emitting electrons, and a first grid and a second grid having respective apertures for converging the electrons emitted from the cathode into a fine electron beam. The aperture of the second grid is sufficiently smaller than that of the first grid and plays an important role for the formation of the electron beam. The electron beam scans a target carrying a charge pattern corresponding to the luminous intensity of an object. Voltages applied to the first and second grids are controlled so as to provide the electron beam quantity corresponding to the luminous intensity of the object forming the charge pattern of the target.

We claim: 
     
       1. A television camera tube device comprising: a target disposed adjacent to one end of a camera tube to produce a charge pattern corresponding to the luminous intensity of an object;   an electron gun disposed adjacent to the other end of the camera tube to generate an electron beam for scanning said target, said electron gun including a cathode emitting electrons, a first grid disposed between said cathode and said target to be applied with a first predetermined voltage and having a first aperture, and a second grid disposed between said first grid and said target to be applied with a second predetermined voltage and having a second aperture smaller than said first aperture; and   means for controlling the voltages applied to said first and second grids for providing the electron beam quantity corresponding to the luminous intensity of the object forming the charge pattern on said target;   wherein the voltages applied to said first and second grids are both positive relative to said cathode, and said voltage control means decreases the voltage applied to said first grid and increases the voltage applied to said second grid, so that a drive curve changes substantially rectilinearly relative to an increase in the luminous intensity of said object.   
     
     
       2. A television camera tube device as claimed in claim 1, wherein the first predetermined voltage applied to said first grid lies within the range of 10 V and 50 V, and the second predetermined voltage applied to said second grid lies within the range of 100 V and 300 V. 
     
     
       3. A television camera tube device comprising: a target disposed adjacent to one end of a camera tube to produce a charge pattern corresponding to the luminous intensity of an object;   an electron gun disposed adjacent to the other end of the camera tube to generate an electron beam for scanning said target, said electron gun including a cathode emitting electrons, a first grid disposed between said cathode and said target to be applied with a first predetermined voltage and having a first aperture, and a second grid disposed between said first grid and said target to be applied with a second predetermined voltage and having a second aperture smaller than said first aperture; and   means for controlling the voltages applied to said first and second grids for providing the electron beam quantity corresponding to the luminous intensity of the object forming the charge pattern on said target;   wherein the voltages applied to said first and second grids are both positive relative to said cathode, and said voltage control means includes arithmetic processing means for receiving and arithmetically processing a signal derived from said target, which signal is indicative of the luminous intensity of said object, and a signal derived from a cathode resistor connected between said cathode and ground; means for superposing a negative voltage corresponding to the output of said arithmetic processing means on the voltage applied to said first grid; and means for superposing a positive voltage corresponding to the output of said arithmetic processing means on the voltage applied to said second grid.   
     
     
       4. A television camera tube device as claimed in claim 3, wherein said arithmetic processing means is a idfferential amplifier. 
     
     
       5. A television camera tube device comprising: a target disposed adjacent to one end of a camera tube to produce a charge pattern corresponding to the luminous intensity of an object;   an electron gun disposed adjacent to the other end of the camera tube to generate an electron beam for scanning said target, said electron gun including a cathode emitting electrons, a first grid disposed between said cathode and said target to be applied with a first predetermined voltage and having a first aperture, and a second grid disposed between said first grid and said target to be applied with a second predetermined voltage and having a second aperture smaller than said first aperture; and   means for controlling the voltages applied to said first and second grids for providing the electron beam quantity corresponding to the luminous intensity of the object forming the charge pattern on said target;   wherein the voltages applied to said first and second grids are both positive relative to said cathode, and said voltage control means includes means for receiving and arithmetically processing a signal derived from said target, which signal is indicative of the luminous intensity of said target; means for superposing a negative voltage corresponding to the output of said arithmetic processing means on the voltage applied to said first grid; and means for superposing a positive voltage corresponding to the output of said arithmetic processing means on the voltage applied to said second grid.   
     
     
       6. A television camera tube device as claimed in claim 5, wherein said arithmetic processing means is a non-linear amplifier. 
     
     
       7. A television camera tube device as claimed in claim 5, wherein the first predetermined voltage applied to said first grid lies within the range of 10 V and 50 V, and the second predetermined voltage applied to said second grid lies within the range of 100 V and 300 V. 
     
     
       8. A television camera tube device as claimed in claim 1, wherein said cathode is of an impregnated type.